League of Denial: The NFL, Concussions and the Battle for Truth by Mark Fainaru-Wada and Steve Fainaru:
McKee and her colleagues had used their platform to become increasingly assertive about the dangers of football. One of their most ominous assertions was that full-blown concussions weren’t what was triggering the disease. Rather, McKee and her group believed that CTE was essentially dementia pugilistica—boxer’s dementia—now being found in other contact sports, especially football and hockey. As in boxing, it was the accumulation of hundreds or thousands of “subconcussive” blows that caused the damage, not one big knockout punch or open-field collision. “We don’t think it’s because of direct blows,” McKee said. “This is a very internal part of the brain. I mean, it’s really deep inside.” Cantu called CTE “a dose-related phenomenon” involving “total brain trauma.”
These assertions had obvious implications for the NFL. The league could change the rules to cut down on helmet-to-helmet hits. It could monitor the number of concussions in an effort to reduce them. It could put independent neurologists on the sidelines to look for concussions and try to end the culture of pain that pressured players to play through it. But if CTE was occurring at a deeper level, as the BU Group believed, that raised questions about the very essence of football.